1. Field of the Invention
The present invention relates to a projection device and an image correction method.
2. Description of the Related Art
A projection device such as a projector device is known which drives display elements based on an input image signal and projects an image relating to the image signal on a projection face of a projection medium such as a screen or a wall face. In such a projection device, in a case where a projection image is projected not in a state in which an optical axis of a projection lens is perpendicular to the projection face but in a state in which the optical axis of the projection lens is inclined with respect to the projection face, a problem of a so-called trapezoidal distortion in which a projection image projected in an originally approximate rectangular shape is displayed to be distorted in a trapezoidal shape on the projection face occurs.
Accordingly, conventionally, by performing a trapezoidal correction (keystone correction) for converting an image that is a projection target into a trapezoidal shape formed in a direction opposite to the trapezoidal distortion occurring in the projection image displayed on the projection face, a projection image having an approximately rectangular shape without any distortion is displayed on the projection face.
For example, in Japanese Patent Application Laid-open No. 2004-77545, a technology for projecting an excellent video for which a trapezoidal distortion correction has been appropriately performed onto a projection face in a projector also in a case where the projection face is either a wall face or a ceiling is disclosed.
More specifically, in Japanese Patent Application Laid-open No. 2004-77545, a technology is disclosed in which, in a case where a video is projected while moving the video in the vertical direction, when an inclined angle from a reference position, which relates to the vertical direction, of an inclining mechanism unit supporting a video projection mechanism unit projecting the video to be rotatable in the vertical direction becomes a predetermined inclined angle set in advance, the degree of correction at the time of performing a trapezoidal correction for video data corresponding to a video is changed by reversing the upper side and the lower side of the trapezoid.
In addition, in Japanese Patent Application Laid-open No. 2004-77545, a technology is disclosed in which, in a case where a video is projected while being moved in the horizontal direction, when a displacement angle displaced from the reference position, which relates to the horizontal direction, of a rotation mechanism unit that supports the video projection mechanism unit projecting a video to be rotatable in the horizontal direction becomes a predetermined displacement angle set in advance, the degree of correction at the time of performing a trapezoidal correction of video data corresponding to a video is changed by reverting the left side and the right side of the trapezoid.
Meanwhile, in Japanese Patent Application Laid-open No. 2004-77545 described above, in a case where the projection position on a projection medium is moved while the video is continued to be projected, the kind of the trapezoidal correction performed on each corner of the projection medium and the kind of video to be projected are not disclosed.
In other words, for example, when a video is continuously projected while the projection position is changed from the front wall portion of the projection medium to the ceiling portion, in a case where a corner of the front wall portion and the ceiling portion is included in the projection range of the projected video, the kind of the trapezoidal correction to be performed and the like are not disclosed. The same is true of the case of a corner of the front wall portion and the side wall portion. Only it is disclosed that the degree of a correction for the projected video is switched between before and after a predetermined displacement angle set in advance in a non-continuous manner.
Thus, in a case where the projection position on the projection medium is changed while the projection of the video is continued, according to the technology disclosed in Japanese Patent Application Laid-open No. 2004-77545 described above, in a case where the projected video is positioned at the corner (for example, a corner of the front wall portion and the side wall portion or a corner of the front wall portion and the ceiling portion) of the projection medium, a problem in that the shape of the projected video changes in a non-continuous manner before and after the above-described predetermined displacement angle set in advance is supposed to occur.
For example, in a case where the projection position of the video is changed from the front wall portion to the ceiling portion, the video positioned at the corner is projected for up to the predetermined displacement angle such that a portion projected to the front wall portion has a rectangular shape, and a portion projected to the ceiling portion with the corner formed as the boundary has a trapezoidal shape. Then, after the predetermined displacement angle, a video is projected such that a portion projected to the front wall portion has a trapezoidal shape, and a portion projected to the ceiling portion with the corner formed as the boundary has a rectangular shape. In other words, between before and after the predetermined displacement angle, the shape of the projected video changes in a non-continuous manner.
In addition, in a case where the projection image reciprocates over the corner of the projection medium or in a case where the movement of the projection image is stopped at the corner limit, the forward/backward conversion of the trapezoidal correction is repeatedly performed, and the shape of the projected video repeatedly changes in a non-continuous manner in accordance with the repeated conversion, and accordingly, the occurrence of a problem in that the projection image becomes unstable may be supposed.
As above, according to the technology disclosed in Japanese Patent Application Laid-open No. 2004-77545 described above, at the corner of two projection faces of the projection medium such as a wall face and a ceiling face lined up to have a predetermined angle therebetween, that is, at the boundary between two projection faces, the occurrence of a problem in that it is difficult to project a smooth and stable projection image that is easily viewable for an observer is supposed.